Field of the Invention
The present invention relates to an optical field, and more particularly, to a method and an apparatus for forming a high-resolution optical focus and realizing near-field imaging.
Description of the Related Art
Traditional optical technology may not manipulate a near field essential to form an ultrahigh-resolution image or focus due to unique characteristics of light such as refraction and scattering, because it does not break diffraction limits according to Abbe's Law only with a conventional microscope and an object lens. A near field decays exponentially with distance as light is diffracted, and accordingly a near-field scanning optical microscope (NSOM) is developed due to limits of conventional equipment. NSOM technology for inspection of a sample with an about one hundred-nanometer opening for passage of light has many problems. Since the opening needs to physically come in direct contact with the sample to be measured, the technology is available to only for limited samples. Moreover, as the opening of an NSOM tip becomes smaller, a mode for passage of light disappears, and thus effective transmission of the light is impossible. In addition, light emitted from an ultra-small light source for measurement may be distorted by the NSOM tip, and an entire area of the sample to be measured is scanned with the NSOM tip, making it impossible to realize imaging in real time. To overcome these problems, a new area of plasmonics is recently on the rise. In plasmonics, however, a surface design is essential between a special metal and a dielectric, and a location of an ultrahigh-resolution focus is fixed by a manufacture material. Furthermore, the NSOM has a severe limit that an impractical increase in incident light is needed so as to obtain higher resolution, in addition to requiring that the small-size opening naturally and physically reach a target spot.
Nanotechnology currently on the rise is realized in two ways, which are divided into a bottom-up method using chemical synthesis and a top-down method using patterning such as lithography. Chemical synthesis may produce limited structures and is still not appropriate for constructing nano-devices widely used in the modern society, that is, electronic circuits. On the contrary, patterning such as lithography enables manufacture of large-area nanostructures and is in use for manufacturing various electronic chips for enabling the information society.
However, technology of manufacturing electronic circuits as one of ground forces for the modern society faces a huge obstacle that optical lithography used for nano-patterning is under the Abbe's diffraction limit. To overcome the obstacle, a smaller wavelength of light, that is, ultraviolet rays, is used, but due to increasing production costs and absence of scalability of the technology, a new technique is absolutely needed at this time.